Tube for boiler economizers, heat exchangers, and the like



Aug. 15, I R 5 B N I TUBE FOR BOILER ECONOMIZERS, HEAT E XCHANGERS, AND THE LIKE Original Filed Jan. 21. .1929

22 .1! 2 R 9 i5 (:4 a5 a al al a a T \f A I zgww Patented Aug. 1 5, 1933 TUBE FOR BOILER ECONOMIZERS, HEAT EXCHANGERS, AND THE LIKE Roger Stuart Brown, Chicago, Ill.

Original application January 21, 1929, Serial No. 333,890. Divided and this application January 2, 1932. Serial No. 584,395

11 Claims. (01. 257 -263) This invention relates to improvements in tubes used in boiler economizers, superheaters, air heaters, oil heaters, or other heat exchangers for heating or cooling various liquid, gaseous, or solid media. It will be realized that I do not wish to limit myself, except so far as set out specifically in the claims, to any particular use of the invention, it being adaptable to a wide variety of uses. However, I have herein illustrated it chiefly in connection with economizer tubes, which disclosure will be at least illustrative of the applications to which the invention may be put. The present application is a division of my copending application 333,890, filed January 21, 1929 which has since matured into Patent No. 1,870,669, August 9, 1932. 1

One object of my invention is to obtain a greater heat transfer per square foot of tube surface,

thereby obtaining greater capacity from apparatus of a given size or area of tube surface or volume of the assembled tubes. This results in a reduced investment in the apparatus itself, and the space required to house it. Another object is to lessen or minimize the draft resistance, for example, by forming the exterior of the tubes to eliminate the tortuosities of the passage or path traveled by the gases. Thus by arranging the tubes in parallel closed columns with space between the columns, and making the sides of the tubes with relatively flat surfaces, straight channels are produced between them for the passage of the. gases, whichfor a given velocity of flow results in a lower draft loss through the apparatus.

A further object attained in some applications of my invention is the maintenance of a considerable reservoir of heat, as by the employment of a large amount of metal which may be held at a relatively high temperature, thus providing a boiler better able to meet fluctuating demands upon it.

Other objects of my invention will appear from time to time in the course of the specifications and claims. I illustrate my invention more or less diagrammatically in the accompanying drawing, wherein- Figure 1 is a transverse section through a bank of tubes arranged in closed column formation with space between the columns.

Figure 2 isa transverse section through one of these tubes of which Figure 3 is a longitudinal elevation, showing end connection.

Figure 4 is a longitudinal section showing an- 55 other end connection.

Figure 5 is a transverse section through a variant tube of which Figure 6 is a longitudinal section.

Figure '7 is a transverse section through another variant tube and Figure 8 is a transverse section through a further variant tube.

Figure 9 is a horizontal longitudinal section through two tubes showing a variant method of applying transverse fins.

Referring to Figure 1, I illustrate such an arrangement of the tubes shown in Figures 2 and. 3 that the outside surfaces G form channels G3 between a column of tubes, these channels being of substantially equal cross-section at right angles to the passage of the gases. It does not affect the utility of my invention if the centers be staggered in the direction as shown in the column at the right of the figure. The centers of successive tubes in the direction of the gas flow may lie in an approximate straight line. This is contrary to the arrangement of a staggered bank of tubes with open columns as illustrated in Figure 1 of my co-pending application No. 333,890.

In Figures 1, 2 and 3, G is a round inner tube, preferably of steel and surrounded by an outer jacket tube G This outer jacket tube is preferably made of cast iron but may be made of other suitable material and is preferably shrunk or pressed onto the outside of the inner tube G. It may, however, be screwed on, clamped, cast, welded, or otherwise positioned about the inner tube. The outer tube, G is made with surfaces, G so designed as to form channels between adjacent columns of tubes and preferably to form a uniform straight channel G between tubes. Each outer jacket, G is shown as having cutaway portions G employed for weight reduction .and to bring the parts G together. It also aids in conducting the heat from the extreme corner of the portions G to the tube G. The outer jacket G is preferably made in a series of short sections placed end to end. It will be understood that the outer piece need not in all cases extend the entire length of the tube, but may terminate short of it as shown for example where the projecting portion of the tube G passes through an aperture in the return fitting F in Figure 3; The jacket encloses the surface available for heat-transfer on the outside of the tube. I may provide it with a series of fins G5 which project from the gas swept surface G and in planes substantially parallel to the direction of the gas travel, which usually will be perpendicular to the longitudinal axis of the tube.

The fins may extend an equal distance outwardly from each side of each outer jacket G or they may extend from one side only of each jacket, or fins of unequal extension may extend from the opposite sides of each jacket. I prefer, however, .that whether fins of equal dimension are formed on each side of the jacket, as shown in Figures 1 and 2, or whether some one of the above arrangements is employed, the fins extend substantially across the passage, defining rectilinear passages for the gases passing therethrough. In the form shown in Figure 1, I employ fins of equal extension on the opposite sides of each jacket member G the fins of adjacent jackets contacting or closely approaching end to end, and each stack of tubes. The outer edges of these fins are also shown as closely approaching but not in contact. They may contact or they may not, in either case defining generally closed rectilinear gas passages. The fins on opposite sides of the same jacket may be staggered, if desired, as shown in Figure 9. This makes possiblea tremendous fin area in a narrow passage. This is in contrast to the form of Figure 1 in which the edges of the fins on opposite sides of the same gas passage abut, leaving only sufficient clearance for expansion and growth. Vertically the tubes may be stacked and carried on these fins. The fins are not in any sense bafiles, and do not substantially change the direction of the g as flow. In Figure 4 I show a tube with inner a1 .d outer portions of equal length, the inner one welded as at G to the return fitting F.

In Figures 5 and 6 I illustrate a variant form of tube in which a continuous cut-away portion G of the previous figures is replaced by a series of transverse webs or tie members, K structurally they may be replaced by clamping bolts to hold the portions G in close contact with the inner tube G.

Referring to the form of Figures 5 and 6, it will be noted that the length of the smooth sides G of the tubes in the direction of gas travel is perceptibly greater than the width of the tube between opposite smooth surfaces G have as much heating surface as the other variations.

Figure 8 illustrates a variant form of tube in which one face of the jacket G is given a convex surface I and the opposite face is given a concave surface I Preferably the radius of the concave section is greater than the radius of the convex by the width of the channel G between them when assembled. v When therefore tubes of form figure 8-are assembled in parallel columns with alternate vertical tubes in a column alternately turned 180 to each other in the positions shown, the bank will form channels between columns of substantially equal width between surfaces, andthese channels will have walls defining gently meandering passages through the bank of tubes. I

The use and operation of my invention are as follows:

I have earlier described an open column arrangement in which the tubes in adjacent columns are in staggered arrangement, andin which adjacent tubes in each column are spaced apart. Each stream of medium circulating between adjacent tubes must, after passing between two adjacent tubes divide and flow around a tube. In other words the streams into which the medium is divided by the tubes about which the medium passes are continuaully being, split and reunited, as the medium flows through the openings between the tubes. I have described above an arrangement of tubes in closed columns, with space between adjacent columns but with little or no space between adjacent tubes in a given column. With the tubes arranged in this closed column relationship, a given stream flows entirely between the same pair of columns and flows past the individual tubes of each column but cannot cross over into a space on the opposite side of either column of tubes by which it is bounded. If round tubes are employed in closed column, the outward medium contacts a relatively small part of the outer tube surface and since the channel or passage first widens and then narrows, an excessive draft loss might result. I therefore form my tubes in such fashion that the tube sides define a smooth walled channel between adjacent columns. The outer medium, for example furnace gases in an economizer, is in contact with a tube surface throughout its passage by a given tube. By taking advantage of the lessened resistance, a given draft can be made to produce a greater velocity, for example by narrowing the space between adjacent tube columns. This results in an increased heat transfer and a greater capacity or efficiency for an apparatus of given size.

My invention permits of the construction of a heat exchange apparatus, for example an economizer or feed water heater for a steam boiler, having all the advantages of a plate type heater, namely straight gas passages, and the principal advantage of tubular heaters, namely the possibilityof heating a liquid or steam under great pressure. This makes a most efficient and compact arrangement in a bank of tubes arranged in closed columns, with space between the columns, an arrangement heretofore regarded as hopelessly inferior to a staggered row arrangement. The arrangement herein proposed permits the use of a steel tube to hold the liquid or steam under pressure, to which it is best adapted, and also permits the use of a cast iron jacket or outer covering for absorbing heat from the furnace gases, whose corrosion it is best adapted to resist.

For purpose of illustration I have described my invention as applied to an economizer for a steam boiler, with water inside of the tubes and the products of combustion from the furnace circulating between the tubes. It will be understood that my invention may be employed regardless of what medium is inside and what outside the tubes and regardless of which medium is the hotter, or what position the bank of tubes is in, or how connected.

It will be realized that whereas I have described and shown a practical and operative device, and have illustrated various modifications and applications thereof, I do not wish to be limited specifically to the forms herein described and shown except so far as I limit myself by the language of my claims. I wish my descriptions and drawing to be taken as in a broad sense illustrative and diagrammatic, rather than limiting me precisely to the details shown. It will be understood that my arrangement may employ rectilinear bounding walls, as shown in Figures 1 and 9 or curvilinear bounding walls as shown in Figure 8. Fins may extend into the gas passages, as shown in Figures 1 and 9, or fins may be omitted, as shown in Figures 5 to 8 inclusive. A composite tube with an inner tube G and an outer jacket G may be employed, as shown in Figures 1 and following, or a simple or single tube may be employed as shown in Figures '7 and 8. The fins may be arranged edge to edge, as shown in the form of Figures 1, 2 and 3, or the fins may overlap as shown in Figure 9. It will be understood that in each form the travel of the gas or fluid along the fins is in parallel with the fins and the fins are not intended to have and do not have a baffling action. Whereas I have shown the fins as at right angles to the long axes of the tubes, such arrangement is a matter of convenience. What is important is that .the fins should be in parallelism with the path of how of the adjacent gases or fluid. If the tubesare arranged at an angle, the fins could still be arranged in parallelism with the flow, even though this involved an angular relationship between tube and fins different than the right angular relation shown in Figures 1, 2, 3 and 9. I

It is characteristic of my invention that the tubes are arranged in closed series, adjacent series defining passages which are continuous past a plurality of tubes in a given series. It may be preferable to have the series forms precisely rectilinear alignments of tubes. Under some circumstances, however, it may be desirable to stagger or otherwise disalign the tubes of the series, the exteriors still forming the characteristic passageways of my invention.

Referring for example to Figures 5 and 8 it will be noted as in Figure 5 that the surfaces (l are of greater width along the direction of flow of the gas than the width between said surfaces across the individual tube. Similarly, in Figure 8 the surfaces I are of greater length than the space between the surfaces I and I of the individual tube. It will be understood that this lengthening of the heat transferring surfaces in relation to the width of the tube may be employed with any form of tube herein shown and that such lengthening tends to increase the efficiency of the heat transfer of the tubes.

I claim:

1. A bank of tubes for heat exchangers and the like, each tube including an interior cylindrical tube, and a separately formed exterior jacket tube positioned thereabout in heat conductive re lationship therewith whose sides define passageways of approximately equal width at points along the line of gas travel between the banks of tubes, such measurement being normal to the surfaces.

2. A bank of tubes for heat exchangers and the like whose sides, when arranged in closed series, define substantially continuous smooth passageways between adjacent series of tubes, the sides of said passageways being provided with a plurality of parallel fins in planes parallel to the flow of the medium circulating between and generally transverse to the banks of tubes, each such tube having a cylindrical walled interior passage.

3. A bank of tubes for heat exchangers and the like whose sides, when arranged in closed series, define substantially continuous smooth passageways between adjacent series of tubes, the sides of said passageways being provided with a plurality of parallel fins in planes parallel to the flow of the medium circulating between and generally transverse to the banks of tubes, each of said tubes being provided with a separately formed interior cylindrical tube member and an exterior non-cylindrical structure in effective heat conductive relationship with the interior tube member.

4. A plurality of tubes for heat exchangers and the like, each said tube having a cylindrical walled inner passage and a plurality of plane outer surfaces positioned on opposite sides of the tube, said walls being arranged in closed series, the opposed faces of opposed tubes of adjacent series defining generally rectilinear substantially closed passages.

5. A plurality of tubes for heat exchangers and the like, each said tube having a cylindrical walled inner passage and a plurality of plane outer surfaces positioned on opposite sides of the tube, said walls being arranged in closed series, the opposed faces of opposed tubes of adjacent series defining generally rectilinear substantially closed passages, and fins projecting into said passages from adjacent tube surfaces, said fins defining planes parallel with the direction of movement of gasesor fluids through said passages generally transverse to the tubes.

6. In heat exchangers and the like, a plurality of tubes arranged in parallel close series, each said tube having an inner passage member and an outer member having a plurality of smooth surfaces located on opposite sides of the tube, said surfaces defining closed passages between tube series of generally constant width between series, and fins projecting into said passages from adjacent tube surfaces, said fins defining planes parallel with the direction of movement of gases or fluids through said passages, and extending from the opposed walls defining each passage.

7. A plurality of tubes for heat exchangers and the like,each said tube having a cylindrical walled inner passage and a plurality of plane outer surfaces positioned on opposite sides of the tube, said walls being arranged in closed series, the opposed faces of opposed tubes of adjacent series defining generally rectilinear substantially closed passages, and fins projecting into said passages from adjacent tube surfaces, said fins defining planes parallel with the direction of movement of gases or fluids through said passages, said fins extending from the opposed walls defining each passage, the fins on said opposed walls being in staggered relationship.

8. In heat exchangers and the like, a plurality of separate tubes arranged in close parallel series, the individual tubes of each series having cylindrical interiors and individual exterior structures in effective heat conducting relationship with the tube, the exteriors of said structures having generally smooth surfaces on a plurality of opposite sides, said smooth surfaces of adjacent tubes of adjacent series defining substantially closed passageways between said series, said passageways being of substantially constant cross-section.

- 9. In heat exchangers and the like, a plurality of separate tubes arranged in parallel series, the individual tubes having cylindrical interiors, the exteriors of said tubes having plane surfaces on a plurality of opposite sides, such plane surfaces defining planes parallel to each other, the opposed plane surfaces of adjacent tubes of adjacent series defining substantially closed passageways between said series, said passageways being of substantially constant cross-section, the adjacent tubes of the individual series having their opposed faces substantially spaced apart intermediate the edges of said faces, the edges of said opposed faces being closely adjacent to each other along the passageways between said series.

10. In heat exchangers and the like, a plurality of tubes arranged in generally parallel series,

ries. the individual tubes having cylindrical interiors, individual exterior structures associated with each tube in effective heat conducting relationship, said structures having smooth exterior surfaces on a plurality of opposite sides, the smooth surfaces of adjacent series defining closed passageways between said series of substantially uniform width between series, the length of the smooth sides of the tubes in the direction of gas travel being greater than the width of the tube between opposite smooth surfaces.

ROGER STUART BROWN. 

